Regulators approve Google's acquisition of Motorola Mobility, its last major hurdle, but with conditions to protect the OS.

Google has cleared the final major hurdle to its acquisition of Motorola Mobility, gaining approval from Chinese regulators - but on condition it keeps Android free and open for at least five years.

It seems that the Chinese regulators, the final international authority to have to green-light the deal, are keen to ensure that Google cannot create advantages for its new handset arm, or limit access to Android for other OEMs such as China's own ZTE and Huawei.

Google itself recently outlined a new approach to Android devices, under which it will expand the range of own-branded Nexus products to include more partners and try to boost a direct-to-consumer distribution route that would reduce the role of carriers.

Although that seems designed to reassure partners that Motorola will not have special treatment, or be the exclusive Nexus vendor, it also appears to create an inner circle of about five OEMs which would gain early access to new Android features, plus the might of Google's marketing machine.

Google faces a difficult balancing act between the volumes that come with full Android openness, and the need to improve quality of experience and reduce fragmentation, goals which point to greater control of the devices.

However, the search giant's executives have been vocal about keeping Android fully open source. When the Motorola deal was announced, CEO Larry Page said: "Many hardware partners have contributed to Android's success and we look forward to continuing our work with all of them on an equal basis to deliver outstanding user experiences. We built Android as an open source platform and it will stay that way."

But Google has at least half an eye on Apple's hardware/software model. It has rebranded Android Market under its own name, as the Google Play multimedia hub, and looks to tie devices more tightly into services like Google+ to drive cloud and content revenues. That in turn is likely to boost Android partners' efforts to differentiate their products via their own content stores and user interfaces, as seen at Samsung and HTC.

Motorola Mobility said in a statement: "We are pleased the deal has received approval in all jurisdictions. We expect to close imminently." The $12.5bn deal has already been approved in Europe and the US, and other jurisdictions.